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J Cell Biol December 15, 2008; 183 (6): 1007-17.

CaM kinase II initiates meiotic spindle depolymerization independently of APC/C activation.

Reber S , Over S , Kronja I , Gruss OJ .

Altered spindle microtubule dynamics at anaphase onset are the basis for chromosome segregation. In Xenopus laevis egg extracts, increasing free calcium levels and subsequently rising calcium-calmodulin-dependent kinase II (CaMKII) activity promote a release from meiosis II arrest and reentry into anaphase. CaMKII induces the activation of the anaphase-promoting complex/cyclosome (APC/C), which destines securin and cyclin B for degradation to allow chromosome separation and mitotic exit. In this study, we investigated the calcium-dependent signal responsible for microtubule depolymerization at anaphase onset after release from meiotic arrest in Xenopus egg extracts. Using Ran-guanosine triphosphate-mediated microtubule assemblies and quantitative analysis of complete spindles, we demonstrate that CaMKII triggers anaphase microtubule depolymerization. A CaMKII-induced twofold increase in microtubule catastrophe rates can explain reduced microtubule stability. However, calcium or constitutively active CaMKII promotes microtubule destabilization even upon APC/C inhibition and in the presence of high cyclin-dependent kinase 1 activity. Therefore, our data demonstrate that CaMKII turns on parallel pathways to activate the APC/C and to induce microtubule depolymerization at meiotic anaphase onset.

PubMed ID: 19064669
PMC ID: PMC2600749
Article link: J Cell Biol

Genes referenced: aurka btg3 camk2g ccnb1.2 cdk1 gnao1 ran tpx2

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References [+] :
Blower, A Rae1-containing ribonucleoprotein complex is required for mitotic spindle assembly. 2005, Pubmed, Xenbase

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